1. Technical Field
The present disclosure relates to an oscillation signal generation circuit that operates in a high frequency band exceeding 100 GHz.
2. Description of the Related Art
In recent years, with an increase in the use of the wireless technology typified by communication and radar, a frequency has rapidly become scarce. For this reason, a frequency band exceeding 100 GHz which is a frequency higher than a millimeter waveband is expected to be utilized. Thus, it is anticipated that a wireless integrated circuit (IC) that operates in a frequency band exceeding 100 GHz will be widely used.
In general, the wireless IC is often produced by a production method such as a complementary metal-oxide semiconductor (CMOS) process by using a semiconductor as a material. However, the performance of the CMOS process at high frequencies is lower than the performance of other production methods, which makes it difficult to achieve power gain at high frequencies.
Theoretically, the use of the fine CMOS process makes it possible to produce a wireless IC that operates in a frequency band exceeding 100 GHz, but there is almost no design margin. Furthermore, accuracy variations occur between transistors for a frequency band exceeding 100 GHz, the transistors formed by the CMOS process. This makes it necessary for the wireless IC to perform calibration. There is a high possibility that, in particular, a voltage controlled oscillator (VCO) which is one of the component elements of the wireless IC does not meet an oscillation condition due to the accuracy variations between the transistors. Therefore, a calibration technique for the VCO is important in developing a wireless IC that operates in a frequency band exceeding 100 GHz.
For example, in IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 42, NO. 9, SEPTEMBER 2007, a configuration having a VCO and a calibration circuit that controls the oscillation condition of the VCO is disclosed. The calibration circuit disclosed in IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 42, NO. 9, SEPTEMBER 2007 detects a current value which is the oscillation condition by controlling a current value flowing through the VCO in accordance with an oscillation signal of the VCO.